1. Field of the Invention
The invention relates to a method of steering a road vehicle with front-wheel steering, which has a wheel base 1 (in m), a front cornering stiffness c.sub.v (in N/rad), a center of gravity distance l.sub.h (in m) from the rear axle and a mass m (in kg), wherein by an integrating feedback of a yaw rate signal to the front-wheel steering the yaw movement is decoupled from the lateral movement of the front axle.
2. Description of the Prior Art
In a controlled steering the steering angle is not dictated solely by the driver via the steering wheel; on the contrary, steering movements are superimposed which arise from feedback of measured quantities of the steering dynamics. A requirement is therefore an active steering in which the steering angle is set by a (hydraulic or electric) motor. Active steering systems have already been tested in test vehicles (cf. for example W. Darenberg, Automatic tracking of motor vehicles, Automobilindustrie 1987, pages 155 to 159).
In active steering systems the steering motor is usually controlled by a microprocessor which in its steering control algorithm processes both sensor signals and the position of the steering wheel (which is measured for example with a potentiometer tap). A sensor already in production use in road vehicles is a vibration gyroscope for measuring the yaw rate (cf. H. Inoue, H. Harada and Y. Yokaya, All-wheel steering in the Toyota Soarer, Congress "All-wheel steering in automobiles" Haus der Technik, Essen, 3-4.12.1991).
The steering dynamics of road vehicles can be characterized by a transfer function from the steering wheel angle to the lateral acceleration of the front axle. Such a steering transfer function was substantially simplified by DE 40 28 320 in that the influence of the yaw movement on the steering dynamics was eliminated by a decoupling.
However, the remaining steering dynamics are still dependent on the travelling speed because in all known steering systems the transfer function from the steering wheel angle to the lateral acceleration of the front axle varies with the travelling speed. A learner driver must learn this change of the steering dynamics with the travelling speed and become accustomed thereto. An experienced driver is also liable to make erroneous assessments.